What Next for Vertex?

Shares are plunging after the pharmaceutical company announced erroneous results in a cystic fibrosis study.

Just a few weeks ago, Vertex Pharmaceuticals' cystic fibrosis treatment seemed like a panacea for the stock, but on Tuesday a revision of the drug's clinical trial data is sinking shares.

This morning, Vertex (ticker: VRTX) amended its previous, better-than-expected results, announcing that in a clinical trial of its two-drug Kalydeco/VX-809 combination therapy, only 35% of patients saw an improvement in lung function of at least five percentage points, down from the 46% reported earlier this month. (Currently, there is...